Comparative efficacy and LT₅₀ analysis of biopesticides and botanical extracts against Helicoverpa armigera (Hubner) on chickpea under laboratory conditions

Introduction

Chickpea (Cicer arietinum L.) also known as Bengal gram or gram is one of the most important pulse crops grown worldwide and a vital source of dietary protein, carbs, vitamins and minerals especially in developing nations. Chickpea is the third most significant food legume in the world with a production of over 16.5 million tonnes in 2023, mostly driven by India which provides nearly 75% of this amount. India grows chickpeas on 9.9-10 million hectares and produces more than 11 million tonnes, which is vital for the country's food security (FAOSTAT, 2024). Chickpea production in Gujarat has grown significantly, from 6.36 lakh tonnes in 2019-20 to almost 15.63 lakh tonnes in 2024-25, reflecting its growing importance in the state's agricultural sector (Government of Gujarat, 2025). Several biotic and abiotic factors limit the production of chickpea despite its economic importance. Insect pests are considered as one of the key yield limiting elements among the biotic stressors. More than 60 insect species are known to infest chickpea at different crop growth stages. Among these, gram pod borer, Helicoverpa armigera is considered as the most devastating insect pest producing substantial economic losses in the chickpea growing regions of the world. Helicoverpa armigera is a global, extremely polyphagous insect pest that attacks more than 200 cultivated and wild plant species. The pest infects many economically significant crops which include chickpea, pigeonpea, tomato, chilli, cotton, maize, sunflower, tobacco, okra and many vegetable crops (Dhillon et al., 2012; Ahmad et al., 2014) [6,3] . In chickpea, larvae feed on fragile leaves, blooms and developing pods causing direct damage to the reproductive portions of the plant. During its development stage a single larva can kill a significant number of pods and cause a major drop in production. Yield losses under severe infestation may vary from 30 to 90 per cent depending on pest population, crop stage and environmental circumstances. Thus, the insect is considered to be a major limitation to profitable chickpea production. Synthetic chemical insecticides have been the mainstay for managing H. armigera because of their quick action and availability. Chemical pesticides are effective for short-term insect control but their overuse leads to resistance in pests like H. armigera, environmental pollution, loss of natural predators, and health risks. This highlights the need for sustainable pest management alternatives. Biopesticides and botanical insecticides, particularly neem products containing bioactive agents such as azadirachtin, have emerged as eco-friendly solutions in integrated pest management (IPM), effectively reducing the feeding and reproduction of pests including H. armigera. (Srivastava et al., 2011; Ahmad et al., 2015; Kilani-Morakchi et al., 2021) [13, 2, 9] . Considering the economic importance of chickpea and the growing need for eco-friendly pest management strategies, the current investigation was performed to evaluate the comparative effectiveness of selected biopesticides and botanical extracts against Helicoverpa armigera under laboratory conditions and to determine their median lethal time (LT 50 ) values.

Materials and Methods

Experimental Site

The laboratory experiment was carried out in the Department of Entomology, Sardarkrushinagar Dantiwada Agricultural University, Sardarkrushinagar, Gujarat, India during Rabi season of 2025-2026. The present study was conducted to evaluate the efficiency of certain biopesticides and botanical extracts against gram pod borer, Helicoverpa armigera under laboratory conditions.

Experimental Design and Treatments

The experiment was laid out in Completely Randomized Design (CRD) with nine treatments and three replications. The treatments consisted of different biopesticides and botanical extracts along with an untreated control. Details of the treatments are presented in Table 1.

Preparation of Botanical Extracts

Fresh and healthy plant materials of custard apple (Annona squamosa), lantana (Lantana camara), Ipomoea spp., karanj (Pongamia pinnata), and datura (Datura stramonium) were collected and washed thoroughly with distilled water. The leaves were shade-dried and crushed using a sterilized grinder. The extracts were prepared by homogenizing the required quantity of plant material in distilled water and filtering through muslin cloth followed by Whatman No. 1 filter paper to obtain the desired concentration.

Insect Culture

Helicoverpa armigera larvae were collected from chickpea fields and reared in laboratory conditions (Fig. 1). Bioassay studies were conducted with healthy and active larvae. Third instar larvae were maintained at 27 ± 2 °C and 65 ± 5% RH. All treatments were carried out with uniform sized larvae to minimize experimental variation.

Bioassay Procedure

The efficacy of biopesticides and botanical extracts was evaluated by the leaf-dip method. Fresh chickpea leaves were dipped individually in the respective treatment solutions for approximately 10 seconds and allowed to air dry under room conditions. Similar leaves dipped in distilled water served as untreated control. The treated leaves were placed in sterile Petri dishes lined with moist filter paper. Each treatment consisted of ten Petri dishes per replication, with one larva per Petri dish (Fig. 2). Larval mortality was recorded at 24, 48 and 72 hours after treatment. Mortality was assessed based on the inability of larvae to show coordinated movement upon gentle probing. Leaf-dip bioassays are widely employed for evaluating insecticidal toxicity against H. armigera under laboratory conditions.

Recording of Observations 2.6.1 Larval mortality

Larval mortality was recorded at 24, 48, and 72 hours after treatment and expressed as percentage mortality using the following formula:

Per cent mortality (%) = (Number of dead larvae / Total number of larvae) × 100

LT₅₀ Analysis

The median lethal time (LT₅₀) values were estimated through probit regression analysis based on cumulative mortality data following the procedure described by Finney (1971) [7] . Probit analysis is commonly used for estimating lethal response parameters in insect toxicological studies.

Statistical Analysis

The mortality data were subjected to analysis of variance (ANOVA) appropriate for Completely Randomized Design (CRD). Percentage mortality values were transformed using angular (arc-sine) transformation before statistical analysis. Treatment means were compared at the 5 per cent level of significance. Standard error of mean [S.Em. (±)], critical difference (CD) at 5 per cent, and coefficient of variation (CV%) were calculated to assess treatment effects.

Results

Effect of Biopesticides and Botanical Extracts on Larval Mortality of Helicoverpa armigera

Significant differences were identified among the investigated biopesticides and botanical extracts against Helicoverpa armigera under laboratory conditions (Table 2; Fig. 3 4). Overall, the results revealed that NSKE 5% was the most effective treatment in terms of both larval mortality and speed of action, followed by Azadirachtin 10000 ppm. [11,12] . Wakil et al. have demonstrated that neem formulations generated considerable larval mortality and suppressed the larval development of H. armigera under laboratory conditions. Likewise, Dangi et al. (2019) [5] also showed high mortality of third instar H. armigera larvae treated with neem seed kernel extract and neem-based products further confirming the efficacy of neem-derived compounds against pod borer populations. Earlier investigations in chickpea and other pulse crops also support the efficacy of NSKE as reported in the present study. Several researchers reported that NSKE significantly reduced larval population, pod damage and feeding activity of H. armigera and can be successfully incorporated in integrated pest management techniques. Neem based formulations are regarded safer for the environment than conventional insecticides with their minimal mammalian toxicity and less effect on beneficial species. The second most successful treatment was azadirachtin 10000 ppm. The larvae treated with Azadirachtin showed significant mortality and comparatively low LT 50 value due to its effective antifeedant, growth regulating and toxic activities.

Azadirachtin has been found to adversely affect larval growth, pupation, adult emergence, fertility and longevity of H. armigera. Other studies have shown that azadirachtin can also disrupt the activity of digestive enzymes and interfere with the hormonal regulation required for the development of the insect. Among other botanical therapies, Datura leaf extract and Karanj leaf extract demonstrated moderate efficacy against H. armigera larvae. The insecticidal activity may be attributed to presence of alkaloids, flavonoids, phenolics and other secondary metabolites which may have deleterious influence on feeding behaviour and physiological activities of insects. However, the performance was lesser than the neem-based therapies which shows it is less toxic or slower in its impact on the test insect. The LT 50 statistics also demonstrated the efficacy of the drug. NSKE had the lowest LT 50 value, which indicated that it was fast in its toxic action and higher in its insecticidal efficiency. Lower LT 50 often implies a faster mortality response and better bioefficacy of a drug. The somewhat higher values of LT 50 obtained for the other botanical extracts are observed to show a delayed insecticidal activity and worse efficiency under laboratory conditions. Earlier studies have also revealed similar conclusions that neem-based formulations show faster mortality response than other plant derived extracts. The growing issue of pesticide resistance in H. armigera population requires the development of safer and sustainable pest management strategies. Many synthetic insecticides are losing their long-term effectiveness due to resistance developed by H. armigera. Neem based biopesticides offer good potential in such condition, as neem has many mechanisms of action and so development of resistance is less likely. The present findings in general demonstrated that the NSKE 5% and Azadirachtin 10000 ppm had good insecticidal efficacy against H. armigera and can be employed as effective eco-friendly alternatives to the conventional chemical pesticides. Natural enemies can be incorporated into integrated pest management strategies for sustainable chickpea production, reducing environmental problems from the overuse of pesticides. Therefore, NSKE 5% may be recommended as a promising eco-friendly component in integrated management programmes against H. armigera in chickpea.

Conclusion

The present study proved the potential of biopesticides and botanical extracts for the management of Helicoverpa armigera under lab conditions. Among those tested, Neem Seed Kernel Extract (NSKE) 5% was the most effective having the maximum larvae mortality and the lowest LT 50 value showing quick and strong insecticidal activity. Azadirachtin 10000 ppm was the second most effective therapy and was comparable in decreasing larval survival. Moderate efficiency was observed in Datura leaf extract, Karanj leaf extract and Beauveria bassiana however Lantana and Ipomoea leaf extracts were less effective compared. The results suggested that neem-based solutions are promising as ecofriendly alternatives to traditional chemical pesticides for the control of H. armigera. Their use in integrated pest management programmes can aid to achieving sustainable chickpea production by minimising chemical residues, environmental contamination and the risk of insecticide resistance. Therefore, NSKE 5% may be recommended as a promising eco-friendly component in integrated management programmes against H. armigera in chickpea. However, a further study in field circumstances is needed to corroborate the laboratory results and to assess their practical relevance in the large-scale chickpea production.

Declarations

Acknowledgement

AcknowledgementThe authors express their sincere gratitude to the Department of Entomology, Sardarkrushinagar Dantiwada Agricultural University, Sardarkrushinagar, Gujarat, India, for providing the necessary laboratory facilities, infrastructure, and technical support required for conducting the present investigation.

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